1. Field of the Invention
The present invention relates to a method for the contamination-free separation of semiconductor material, and to a device for carrying out the method.
2. The Prior Art
For the production of solar cells or electronic components, for example memory elements or microprocessors, ultrapure semiconductor material is required. Silicon is the most commonly used semiconductor material in the electronics industry. Pure silicon is obtained by thermal decomposition of silicon compounds, for example trichlorosilane, and in this context is often in the form of polycrystalline ingots. The ingots are needed as starting material, for example, for the production of single crystals. For the production of single crystals using the Czochralski method, the ingots firstly need to be comminuted into fragments of about 100 mm. These fragments are melted in a crucible and the single crystal is then pulled from the resulting melt. In the best possible case, the only contamination in the semiconductor material should then be the dopant deliberately introduced into the semiconductor material.
A variety of methods for the separation of the silicon fragments obtained during the comminution procedure are known. In order to prevent contamination during separation due to the screens, etched silicon plates are frequently applied to the screens. Individual screens, for example ones with a hole diameter less than 40 mm, may consist entirely of shaped silicon parts. Screens of this type do, however, have the disadvantage that they wear out or become damaged during the transfer of forces during the separation procedure and need to be replaced. It is not possible to use the screening system while the broken parts are being replaced.
Added to this is the fact that the production of silicon-coated screens as well as silicon screens is expensive. It generally requires the additional deposition of the silicon, mechanical processing during the production of the shaped parts and expensive cleaning thereof, for example by etching with HF/HNO.sub.3. Since no pieces of the coating or of the shaped parts may enter the screened fragments, the latter need to be manually sorted and checked.